July 05,2013
As economies grow in developing countries, more of them are adopting a Western-style diet. That means eating a lot more meat. As a result, the number of industrial or factory livestock farms has increased. But new research is raising health questions about those farms, which treat animals with antibiotics.
Industrial or factory farms raise large numbers of animals often in very confined buildings. Antibiotics are used in the animals’ feed and water – not just to cure illness – but to help speed growth. But there’s a difference between workers on industrial farms and those employed at farms that do not use antibiotics.
Drug-resistant bacteria were found in the noses of industrial livestock workers in the southern U.S. state of North Carolina. These bacteria are commonly called staph. However, no such bacteria were found in those employed on antibiotic-free farms.
North Carolina is a major producer of hogs and poultry. Industrial livestock farms use large confinement buildings, while antibiotic-free farms generally raise animals outdoors on pastureland.
Study co-author Christopher Heaney said concerns had been raised by community groups and researchers, not only in North Carolina, but even earlier in the Midwestern state of Iowa.
“This work built on those community-driven discussions around air pollution and concerns with odor and health and quality of life. There were questions developing about concerns of people, who are working to help produce livestock – questions around exposures that these workers may be experiencing.”
Heaney is assistant professor of Environmental Health Sciences and Epidemiology at the Johns Hopkins Bloomberg School of Public Health. Similar concerns had been raised abroad, as well.
“As scientists, we were following the emerging story in Europe, which had shown that there was a new strain, or a new sequence type, of staph aureus bacteria, with particular drug resistance to methicillin, known as MRSA. And these previous studies in Europe had detected new strains of drug resistant staph aureus from livestock, first among farmworkers and subsequently in hospital and community settings,” he said.
MRSA is found most often in hospitals or other health-related facilities. The U.S. Centers for Disease Control and Prevention says MRSA can contaminate bed linens, bed rails, bathroom fixtures and medical equipment. Symptoms include fever, chills and boils. In severe cases, mortality rates can be as high as 50 percent.
Heaney said, “The workers participating in our study were not experiencing staph infections at the time of the study. But when antibiotic resistant bacteria do cause infections they can be harder to treat. And we do know that staph aureus is an opportunistic pathogen. It can also be present in the absence of any disease or any symptoms.”
Heaney described it as “remarkable” that staph aureus bacteria were not found in the noses of those working on farms not using antibiotics.
“While everyone in the study had direct or indirect contact with livestock, only industrial workers carried antibiotic resistant staph aureus with multiple genetic characteristics linked to livestock. This means that we did not observe that the antibiotic-free workers were carrying these livestock associated strains of staph aureus, as they’re called, with characteristics of antibiotic resistance,” he said.
But why the difference?
“That’s a good question,” he said, “And I think we’re going to need to spend a lot of time in the future developing studies to try and address these questions. We’ve taken some important first steps, but I think we still need to continue to generate information and generate knowledge to help better understand the dynamics of livestock production with versus without the use of antibiotics.”
Some other big unanswered questions include: Are industrial farmworkers – those with staph aureus bacteria in their noses – actually at greater risk of developing an infection? And could livestock-related staph germs find their way into hospitals and communities similar to what happened in Europe? Heaney said that more studies are also needed to answer those questions.